This invention relates to conveying apparatus and most particularly to conveying apparatus which employ a multiplicity of rollers for moving objects.
A special version of powered roller conveyors termed accumulating conveyors have wide applications in the material handling industry. For example, accumulating conveyors are employed in circumstances where it is necessary to convey fragile merchandise and is desirable to avoid the buildup of line pressure when for various reasons further movement of the merchandise is impeded. The collective torque of the continuously rotating rollers could result in damage. Accumulating conveyors provide for a reduction in or a cessation of line pressure in selected regions of the conveyor in response to the impediment.
There are various known mechanical devices used to convert powered roller conveyors or zones thereof into accumulating conveyors, examples of which may be found in U.S. Pat. Nos. 3,770,102 and 3,718,248. All of the example devices in the aforementioned patents employ some means of interrupting the drive mechanism from the rollers. U.S. Pat. No. 3,770,102 describes an inflatable tube which raises and lowers support rollers which in turn raise and lower a powered endless belt against the conveyor rollers. Pneumatic devices of this nature in combination with movable rollers are well recognized in the art of which this patent is but an example.
U.S. Pat. No. 3,718,248 sets forth still another mechanical device in which a pivotable wheel connected to a sprocket is pivotable into and out of contact with the roller conveyors. The major benefit of this particular mechanical device is particularly manifested in the modular nature of the drive unit, i.e. drive wheel, sprocket, and connecting shaft. Ease of assembly and removal are the result. A detriment, however, is the need to provide a variety of moving parts, e.g. rotating sleeves and collars, to accomplish the rotation. Such parts are susceptible to wear and, as an obvious drawback, add to the cost of manufacture.
Another example of a pivotable device is disclosed in U.S. Pat. No. 4,108,303. This device also has the benefits associated with a modular unit, however, the weight of the drive chain is raised and lowered together with the pivotable wheel that engages the conveying rollers. This tends to result in excessive wear of the chain guides and other components of the modular unit.
A further drawback associated with known pivotable wheels employed in accumulating conveyors is the relatively high degree of accuracy that must be maintained in aligning the wheel so that two adjacent conveying rollers are driven by the wheel. Misalignment or uneven wear may cause the wheel to engage only one conveying roller.
It is the paramount object of the present invention to preserve the modular concept of a movable drive unit which can couple and uncouple the power source from the rollers yet simplify the mechanical structure such that a pivoting action and commitant elements needed to provide such action are unnecessary.
The present invention comprises a drive unit supported by a flexing member which biases the drive unit out of engagement with the conveyor rollers and a control unit which, upon command, flexes the flexing member and therefore the drive unit into positive engagement with the rollers.